1. Field of the Invention
The present invention relates to a hybrid powered automobile having a controller that performs a selective drive control using a generator which generates electricity by an engine driving force or battery.
2. Description of the Prior Art
Electric cars have been known that are powered by batteries on board. The electric cars use electricity stored in the battery as a motive power and do not produce exhaust emissions as do the diesel and gasoline engines that use light oil and gasoline as fuel, and thus have found uses in areas where release of emissions is not wanted, such as urban areas. Battery-powered electric cars, however, have drawbacks that it takes many hours to recharge the battery and that they can only travel a distance corresponding to the battery capacity and cannot run a long distance at a stretch.
Under these circumstances, hybrid cars with an engine and a battery aboard are attracting attention in recent years. The engine on board the hybrid powered automobile operates on gasoline, light oil, alcohol or natural gas as fuel to drive a generator to charge the on-board battery with electric energy, which is used for driving the vehicle. Such hybrid powered automobiles are disclosed, for example, in Japanese Patent Laid-Open No. 270603/1991, 317581/1995 and 23504/1995.
The hybrid powered automobiles disclosed in these publications drive the generator by the engine and use electric power produced by the generator to drive the drive shafts.
In the electric car disclosed in the Japanese Patent Laid-Open No. 270603/1991, the drive wheels are driven by a motor powered by a storage battery, which is connected through a charger to the generator coupled to a generator-driving engine. The charger is designed to be chargeable also from an external power source. Further, in this electric car, the engine is operated at all times in an optimum condition considering the production of exhaust emissions and mileage, and the vehicle is driven by the electricity stored in the battery regardless of variations in drive wheel revolutions, running speed and load. This car is not designed to run only on the battery with the engine at rest. Because the engine is driven at all times, this electric car does not abate the production of NOx in exhaust emissions.
The hybrid electric car disclosed in the Japanese Patent Laid-Open No. 317581/1995 generates by a generator as much electric power as is required by the drive motor to reduce the frequency of battery recharge and discharge and thereby prevent possible efficiency degradation due to recharge and discharge. A motor demand output means determines the amount of electricity required by the drive motor and a calculation means calculates the amount of power to be generated according to the demand power of the motor. When the motor demand power is low, the engine load is also low and a control is performed whereby only a part of the cylinders is operated to reduce throttle losses. Based on the calculated amount of generation, the calculation means determines the engine revolution speed and an operation range decision means checks whether the engine revolution speed is within the range of the current operation mode. If the revolution speed is outside the operation range, a mode change means changes the number of cylinders to be operated.
Further, this hybrid electric car, like the above electric car, has the engine operating at all times while the car is running, in order to generate as much electricity as is consumed by the motor.
In the hybrid car disclosed in the Japanese Patent Laid-Open No. 23504/1995, the power supply circuit is designed to drive the engine near the highest efficiency point to reduce exhaust emissions and prevent battery deterioration. A control section detects the vehicle resting state from a car speed signal and a shift position signal supplied from the sensor section. When the battery charge level is lower than a specified level, the engine is driven near the highest efficiency point to generate electricity by the generator and recharge a capacitor to a specified level. With the capacitor recharged to the specified capacitance, the control section stops the engine and turns on a connection switch to recharge the battery from the capacitor. After the recharge is complete, the switch is returned to the original state.
Further, the power supply circuit of the above hybrid car drives the engine near the highest efficiency point when the charge level of the battery is lower than the specified level and, when it is higher than the specified level, stops the engine. The car is driven by the power of the battery.
In the hybrid powered automobile, which operates an on-board engine using gasoline, light oil, alcohol or natural gas as fuel and at the same time runs on electric energy of an on-board battery, it may be considered desirable if the car is designed to run on the electric energy of the battery in areas where release of exhaust emissions from the engine is not preferred, such as tunnels or urban areas, and in other areas, run on the engine. In that case, the hybrid powered automobile needs to choose between the engine and the battery as a motive power and how the switching timing and switching range should be determined is a critical question. As described above, the hybrid car has yet to determine the timing of switching between the engine and the battery as the motive power.